ok so here is the deal, ive been noticing the last while that when i get less than 1/4 of a tank my fuel pressure drops a few psi, showing around 55-56psi, fill the tank, sits at 58psi. (monitored with a scan gauge with the fuel pressure transducer). well today the pump crapped out on me. had a new aem 320 around the shop to i modded the basket and tossed it in. fire the car up, it makes 85psi. confirmed it on a mechanical gauge. pulled the tank back out, thought i blocked the bleed off port on the regulator with the hose, fixed that, tank back in, same deal. tank back out pulled it all apart, i can blow compressed air through the return line through the regulator.

so what have i screwed up? im at a loss. i remember reading about somebody having a similar issue but cant find it for the life of me.

btw, car is a 2005 lsj

 

i guess another option to fix it is putting an aftermarket regulator on like the zzp kit. ive got most of the fittings around the shop to do it. does anyone know how you disable the 05 fuel regulator? cant seem to find any info on it

 

Just went thru all of that on my buddies stockish LS1 Vett powed class 10 desert chassis. Car is only a few months old but motor was a take out. New fuel safe and pump. Car would die when hot and not restart. When cool it worked fine. Pump sounded like it was sucking air and eventually burned out. Replaced the pump, dissembles tank, checked foam and installed a https://www.holley.com/products/fuel...s/parts/12-924. New filters, checked for kinks thinking it's fixed. Next trip same problem but it sounded like the new warrenty pump was failing. The stock GM regulator on this was also a fuel filter and looked like a canister fuel filter. Upgraded to a CBM regulator and problem was solved. His only problem now is his 400hp heavier car can't catch mine unless we stretch the big end way way out.
I do the desert in the winter and boats in the summer so the vehicles sit. The fuel we have today does not like that and causes all sorts of problems. First thing I do on any used buggy or boat is remove and clean the tank, replace filters and all rubber fuel lines, install carb kits and fuel pump rebuild diaphragms. Anything that's not steel and touches fuel gets replaced. Headaches solved. Im not sure what your regulator looks like but yes make it go away.

 

the regulator is a non serviceable part, comes part of the basket assembly. its not that easy to just "make it go away" and keep the basket functioning correctly. the only info on disabling the in tank regulator i could find on an 05 was in the gm build book, their answer is gut everything off it and drill holes in the basket to make sure it fills correctly. we all know how drilling extra holes in the 05 basket turns out....

end result is ive got a new delphi pump assembly on order, should have it this afternoon.

 

Nice thing about stock is it's easy. The adjustable regulator is nice as a tuning tool. I mix race gas or AV gas mixed with 91 3:2 or 4:2 depending on how hot it is. If I pop a little at high RPM when I let off I tweet it. Too bad it's such a pita to add one to your car. 61 psi generally what mine likes because It was tuned on 50/50 mix to be safe at 59 psi. Later I ported the S/C intake for more air. I guess a computer and dyno would be best but you can feel it and tweet it old school really easy.

 

there is a spring and a check ball on the return line inside the canister take it apart and see if the check ball is stuck I have seen it happen before and cause high fuel pressure

 

mine doesnt have a ball and spring, it looks more like a diaphragm regulator. my car is a 2005, its different than the 06+ baskets.

 

Ya you might need a basket from a 06. Any 06+ ion/Balt should Have one.

 

from my reading the 06+ fuel sender works backwards

 

you can swap the sender out